A long list of ISIS names, turned over, by an ISIS traitor.

FOX's Alastair Wanklyn reports:

It's a set of computer files that appear to be membership forms filled out with ISIS fighters' real names and countries of origin and even has phone numbers for their families.

Analysts say it could help to identify Jihadi's, who have now returned to their home countries unnoticed. They say the exposure may discourage other fighters from joining the terror group.

FOX sister network Sky News says it got the data from a defector who left ISIS after he felt it abandoned its Islamic principles.

Alastair Wanklyn, FOX News.